US2765625A - Air-hydraulic booster - Google Patents

Description

C. H. HART AIR-HYDRAULIC BOOSTER Filed June 12, 1952' INVENTOR.

BY Q. 7

Unit States AIR-HYDRAULIC BOOSTER Charles H. Hart, Detroit, Mich.

Application June 12, 1952, Serial No. 293,220 Claims. (Cl. Gil-54.6)

This invention relates to improvements in an air-hydraulic booster unit of the type comprising a pneumatically actuated piston and a hydraulic ram or plunger connected for recriprocation in unison, the ram or plunger having a smaller volume of displacement than the piston and being reciprocable Within a hydraulic chamber, thereby to displace fluid from the chamber at increased pressure with respect to actuating air pressure applied to the piston.

An important object of the present invention is to provide an improved booster unit of the aforesaid nature which is particularly simple and eificient in structure and operation and which provides improved automatic means for replenishing fluid within the hydraulic chamber upon each retraction stroke of the ram or plunger.

Another object is to provide a booster unit of the foregoing nature wherein the reciprocable ram or plunger is movable toward an inlet port on the forward or fluid displacement stroke and is movable from the inlet port on the retraction stroke. A plunger type valve extending longitudinally in the direction of reciprocation and adapted at one end to seat at the inlet port to close the same is slidably mounted on the ram or plunger. A projection on the ram or plunger is arranged to engage and move the valve from the inlet port to open the latter upon retraction of the plunger to a predetermined position adjacent its limit of retraction movement. Upon movement of the plunger beyond said predetermined position in the direction toward the inlet port, the valve is released from said projection for movement toward the inlet port to seat thereat, spring means being employed to urge the valve yieldingly to the seated position. Thus throughout continued movement of the ram or plunger toward the inlet port, the latter is maintained closed by the valve and fluid displaced by the ram or plunger is forced under magnified pressure from the hydraulic chamber. However upon completion of each retraction movement, the inlet port is open to replenish fluid lost from the hydraulic system during the preceding operation.

Another and more specific object of the invention is to provide a particularly compact and eflicient booster unit of the character described having an axially reciprocable plunger movable toward and from the inlet port as aforesaid and provided with an axially extending bore opening toward the inlet port and having said plunger type valve slidably seated therein. The valve in turn is provided with an axially extending bore opening at one end into the bore of the plunger. The other end of the plunger type valve is adapted to seat at the inlet port as aforesaid to close the latter. Secured to the ram or plunger is a spring guide which extends axially into the bore of the valve to position a spring coiled around the guide under compression between the plunger and valve to urge the latter yieldingly toward the inlet port to seat thereat. Spaced apart slightly less than the distance of retraction movement when the plunger is at its limit of movement toward the inlet port are cooperating shoul- 2,765,625 Patented Oct. 9, 1956 ders on the valve and plunger arranged to abut each other upon retraction of the plunger substantially to its limit of movement, thereby to move the valve from the inlet port to open the latter upon completion of the retraction stroke.

Other objects of this invention will appear in the following description and appended claims, reference being had to the accompanying drawings forming a part of this specification wherein like reference characters designate corresponding parts in the several views.

Fig. 1 is a longitudinal median section.through an airhydraulic booster unit embodying the present invention, showing the hydraulic ram or plunger at the limit of its work or displacement stroke.

Fig. 2 is a view similar to Fig. 1 but showing the ram or plunger at the limit of its retraction stro re.

Fig. 3 is a section taken in the direction of the arrows substantially along the line 33 of Fig. 2.

It is to be understood that the invention is not limited in its application to the details of construction and arrangement of parts illustrated in the accompanying drawings, since the invention is capable of other embodiments and of being practiced or carried out in various ways. Also it is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation.

Referring to the drawings, a particular embodiment of the present invention is shown comprising by way of example a two part housing including a hydraulic cylinder 1i and a pneumatic cylinder 11 arranged coaxially end to end with their bores opening into each other. Reciprocable within the cylinder 16 is a hydraulic ram or plunger 12 which is adapted to extend substantially the entire length of the cylinder 10 and rearward partially into the cylinder ii. The diameter of the rear end of the plunger 12 is reduced to provide a seat 13 for a piston indicated generally by the numeral 14 and reciprocable within the cylinder 11. The piston 14 comprises a center plate 15 spaced from forward and rearward outer plates 16 and 17 respectively by forward and rearward piston cup packings 1S and 19 respectively. The latter are supported by their corresponding plates 16 and 17 so as to conform closely to the interior of the air cylinder 11 during pneumatic actuation as discussed below. The forward plate 16 is held snugly against the shoulder at the forward end of the reduced plunger portion 13 by a lock washer 2i) and nut 21 screwed on an externally threaded rear end of the reduced ram portion 13.

The hydraulic and air cylinders 10 and 11 are separated by forward and rearward packing rings 22 and 23 located snugly around the ram or plunger 12 within a rearward enlargement of the bore for the hydraulic cylinder lit The rings 22 and 23 are reinforced by annular support glands 24 and 25 respectively and are spaced by an annular drain member 26. The inner and outer circumferences of the member 26 are provided with annular drain grooves connected by one or more radial ducts 27, the outer drain groove being in turn in communication with a discharge conduit 28 which extends radially through the housing portion 11 to discharge hydraulic fluid that might leak rearward from the cylinder 10. Secured to the forward wall of the air cylinder 11 by screws 29 is an annular retaining gland 3t) overlying the packing 23 to hold the same in position.

By the structure described thus far, the piston 14 and ram 12 are reciproc-able as a unit, so that pneumatic pres= sure applied to drive the piston 14 forward is magnified in the hydraulic cylinder in accordance with the ratio of the cross sectional areas of the piston 14 to the ram or plunger 12. Pneumatic actuation of the piston .14 is achieved by a high pressure port 31 in a rear end closure plate 32, which is secured to the cylinder 11 by bolts 33,

and by a return port 34 in the sidewall of the cylinder 11 forward of the limit of forward movement of the piston 14. The ports 31 and 34 are connected to conduits 35 and 36 respectively within a pneumatic circuit, whereby the piston 14 is selectively driven forward to the position of Fig. l by introducing high pressure air through port 31, or retracted to the rearward position of Fig. 2 by introducing air pressure through port 34 when conduit 35 is connected to exhaust.

The forward end of the hydraulic cylinder is closed by a forward end closure plate 37 secured to the cylinder 10 by a plurality of bolts 38. The plate 37 is provided with a radial inlet conduit 39 in communication at its inner end with an axial inward opening hydraulic port 40. The outer end of the conduit 39 is connected with a conduit 41 which in turn is connected with a source of hydraulic fluid, as for example a water supply under ordinary city water pressure. A radial outlet conduit 42 in the forward end closure plate 37 is connected at its inner end with an axially inward opening hydraulic discharge port 43 and is connected at its outer end with a conduit 44 which extends to the machine or device to be hydraulically actuated, such as a spot welding gun, for example. O- rings 45 and 46 seated within radially outward opening annular grooves in inner offset portions of the rear and forward end closure plates 32 and 37 respectively snugly engage the adjacent inner walls of the cylinders 11 and 10 respectively to provide fluid tight seals thereat.

The hydraulic inlet port 40 opens into the cylinder 10 coaxially with the ram or plunger 12 and is adapted to be closed by the conically tapered forward end of a plunger type valve 47 when the latter is pressed forward, as described below. The stem of the valve 47 extends coaxially rearward into a bore 48 within the ram or plunger 12 and is slidable therein to permit forward movement of the plunger 12 to the limit of movement, Fig. l, as determined by abutment between the gland and piston plate 16. The rear end of the bore within the ram or plunger 12 is closed by a screw plug 49 which supports a spring guide 50 extending coaxially forward within a rearwardly opening bore 51 in the valve 47 The latter is yieldingly urged forward to the seated position to close the inlet by means of a coil spring 52 which extends longitudinally within the bore 51 and around the guide and is under compression between the forward end of the bore 51 and a rear spring retaining washer 52a. The latter is located around the guide 50 near its juncture with the plug 49 and is spaced from the plug by a washer 53.

In order to retract the valve 47 from the port 40, the valve 47 is provided intermediate its ends with a radial shoulder 54 adapted to be abutted by a generally annular mating shoulder 55 of the plunger 12 extending radially inward around the valve 47 adjacent the forward end of the plunger 12. When the piston 14 is at its forward limit of movement, Fig. 1, the shoulders 54 and 55 are spaced apart a distance slightly less than the maximum rearward travel permitted to the piston 14 and plunger 12. Accordingly, just before the piston plate 17 abuts the forward surface of the rear end plate 32, the shoulder 55 moves into abutment with the shoulder 54, causing retraction of the valve 47 from its seated position at the hydraulic inlet port 40 and opening of the latter upon continued rearward movement of the plunger 12. The spring 52 is dimensioned so as to urge the shoulder 54 yieldingly forward toward the shoulder 55 at all positions of the plunger 12. Accordingly upon forward movement of the piston 14 from the rearmost or retracted position, Fig. 2, the valve 47 will move forward with the plunger 12 and shoulder 55 until the tapered end of valve 47 seats at and closes the port 40, whereupon the shoulder 55 continues forward of the position of abutment with the shoulder 54. Hydraulic pressure in the forward end of cylinder 10 and the bore 51 of valve 47 is equalized by means of one or more ports 56 extending axially in the annular shoulder 55 and one or more radial ports 57 through the valve 47.

During normal operation of the booster unit, the duct system 39 through 44 and the portion of the cylinder 10 not occupied by the plunger 12 are maintained full of fluid. During a forward work or pressure stroke of the ram or plunger 12 and after the valve 47 has seated itself at the port 40 to close the same, the fluid displaced from the cylinder 10 by the plunger 12 is forced under pressure to the work stroke via conduit 44. Upon completion of the work stroke, the plunger 12 is retracted and fluid within the duct system 44 backs from the work to fill the cylinder 10. When the plunger 12 almost reaches the rearward limit of the retraction stroke as aforesaid, the shoulders 55 and 54 abut each other, causing retraction of valve 47 and opening of inlet port 40. In the event that hydraulic fluid has been lost from the circuit during the preceding work stroke, the lost fluid is now replenished via port 40. On the next work stroke, fluid is momentarily forced back through port 40 until forward movement of shoulder 54 permits the forwardly spring pressed valve 47 to seat at and close port 40. Thereafter the work stroke is repeated as above.

I claim:

1. In a pressure booster, a low pressure cylinder, a high pressure cylinder, a piston reciprocal in the low pressure cylinder, a tubular plunger reciprocal in the high pressure cylinder and extending rearwardly therefrom into the low pressure cylinder, said plunger being secured to the piston to reciprocate therewith, a fluid inlet port in the forward portion of the high pressure cylinder, a valve seat around said port, a plunger type valve shiftable forwardly against said seat to close said port, a tubular stern connected to said valve to shift therewith and extending rearwardly therefrom into the bore of said plunger and opening rearwardly thereinto, a spring guide secured to said piston to reciprocate therewith and extending for wardly therefrom into the bore of said stem through the rear end thereof, a coil spring within the bore of said stem and around said guide and under compression between said piston and valve to urge the latter forwardly to close said inlet port, mating shoulders on said stern and plunger cngageable to move said valve from said valve seat upon rearward shifting of said piston to adjacent its limit of rearward movement, a radial duct through the sidewalls of said stem adjacent the forward end thereof and connecting the bore of said stem with said high pressure cylinder, fluid passage means extending between the juxtaposed walls of said plunger and stem and connecting said radial duct with said forward portion of said high pressure cylinder when the plunger is at its limit of forward movement, and a fluid outlet port in said forward portion of the high pressure cylinder.

2. In a pressure booster, a low pressure cylinder, a high pressure cylinder, a piston reciprocal in the low pressure cylinder, a tubular plunger reciprocal in the high pressure cylinder and extending rearwardly therefrom into the low pressure cylinder, said plunger being secured to the piston to reciprocate therewith, a fluid inlet port in the forward portion of the high pressure cylinder, a valve seat around said port, a plunger valve shiftable forwardly against said seat to close said port, a tubular stem connected to said valve to shift therewith and extending rearwardly therefrom into the bore of said plunger and opening rearwardly thereinto, the forward end of the bore of the tubular stem being closed by said valve, a spring guide secured to said piston to reciprocate therewith and extending forwardly therefrom into the bore of said stem through the rear end thereof, a coil spring within the bore of said stem and around said guide and under compression between said piston and valve to urge the latter forwardly to close said inlet port, mating shoulders on said stern and plunger engageable to move said valve from said valve seat upon rearward shifting of said piston to adjacent its limit of rearward movement, said stem having a duct connecting its bore with the interior of said high pressure cylinder, axially extending fluid passage means between the juxtaposed walls of said plunger and stem and connecting said duct with said forward portion of said high pressure cylinder when the plunger is at its limit of forward movement, and a fluid outlet port in said forward portion of the high pressure cylinder.

3. A pressure booster having low and high pressure cylinders, the former behind the latter, a piston reciprocal axially within the low pressure chamber, a tubular plunger shiftable axially Within said cylinders and connected to said piston, a fluid inlet port in the forward portion of the high pressure chamber, a valve seat around said port, a plunger type valve shiftable forwardly against said seat to close said port, a tubular stem connected to said valve to shift therewith and extending rearwardly therefrom into the bore of said plunger and opening rearwardly thereinto, said valve closing the forward end of the bore of said stem, said stern substantially filling the bore of said plunger when said piston is at its limit of forward movement, a spring guide secured to said piston to reciprocate therewith and extending forwardly therefrom into the bore of said stem through the rear opening thereof, said spring guide substantially filling the bore of said stern when said piston is at its limit of forward movement, a coil spring around said guide and compressible Within the bore of said stem between said piston and valve to urge the latter forwardly to close said port, said plunger having a portion engageable with a portion on said stem to move said stem and valve rearwardly to open said port upon predetermined rearward movement of said plunger, said stern having a radial duct therethrough opening into the bore thereof, axially extending fluid passage means between the juxtaposed portions of said stern and plunger and connecting said radial duct with the forward portion of said high pressure cylinder when the plunger is at its forward limit of movement, and a fluid outlet port in the forward portion of said high pressure chamber.

4. In a pressure booster, a low pressure cylinder, a high pressure cylinder, a piston reciprocal in the low pressure cylinder, a tubular plunger reciprocal in the high pressure cylinder and extending rearwardly therefrom into the low pressure cylinder, said plunger being secured to the piston to reciprocate therewith, a fluid inlet port in the high pressure cylinder, a valve seat around said port, a plunger type valve shiftable forwardly against said seat to close said port, a tubular stem connected to said valve to shift therewith and extending rearwardly therefrom into the bore of said plunger and opening rearwardly thereinto, a guide secured to said piston to reciprocate therewith and extending forwardly therefrom into the bore of said stem through the rear end thereof, spring means engaging portions fixed with respect to said valve and piston respectively and yieldingly urging said valve forwardly with respect to said piston to close said inlet port, means on said stem and plunger for moving said valve from said valve seat upon rearward shifting of said piston to adjacent its limit of rearward movement, said stem having a duct connecting its bore with the interior of said high pressure cylinder, fluid passage means extending between the juxtaposed walls of said plunger and stem and connecting said duct with said high pressure cylinder when the plunger is at its limit of forward movement, and a fluid outlet port in said high pressure cylinder.

5. In a pressure booster, a low pressure cylinder, a high pressure cylinder, a piston reciprocal in the low pressure cylinder, a tubular plunger reciprocal in the high pressure cylinder and extending rearwardly therefrom into the low pressure cylinder, said plunger being secured to the piston to reciprocate therewith, a fluid inlet port in the forward portion of the high pressure cylinder, a valve shiftable forwardly to close said port, a tubular stem connected to said valve to shift therewith and extending rearwardly therefrom into the bore of said plunger and opening rearwardly thereinto, the forward end of said stem being closed at a location adjacent and rearwardly of said valve, a spring guide secured to said piston to reciprocate therewith and extending forwardly therefrom into the bore of said stem through the rear end thereof, a coil spring within the bore of said stem and around said gude and under compression between said piston and valve to urge the latter forwardly to close said inlet port, means on said stem and plunger for moving said valve from said valve seat upon rearward shifting of said piston to adjacent its limit of rearward movement, said stern having a duct rearwardly of said location connecting the bore of said stem with the interior of said high pressure cylinder, fluid passage means extending between the juxtaposed walls of said plunger and stem and connecting said duct with said forward portion of said high pressure cylinder when the plunger is at its limit of forward movement, and a fluid outlet port in said forward portion of the high pressure cylinder.

References Cited in the file of this patent UNITED STATES PATENTS 1,550,089 Mattingly Aug. 18, 1925 1,593,188 Mattingly July 20, 1926 2,305,638 Rockwell Dec. 22, 1942 2,536,140 Rockwell Jan. 2, 1951

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